Apparatus for the application of a curable composition to a fastener and curable compositions suitable for application to a fastener

ABSTRACT

An apparatus ( 1 ) for the application of a composition curable by irradiation to a fastener ( 2 ) having a conveyor ( 3 ) for conveying fasteners to an application station ( 5 ); an application station ( 10 ) comprising an applicator from which the composition is dispensed. The conveyor rotates the fasteners past the applicator for application of composition. The same or another conveyor ( 8 ) conveys the fasteners to an irradiation station ( 10 ) and rotates the fasteners for irradiation thereof. The irradiation station irradiates and thus cures the composition applied to each fastener.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for the application of acurable composition to a fastener, especially to a threaded fastener. Inparticular, the invention relates to an apparatus for the application ofan at least two stage curable composition to a fastener. The inventionfurther relates to curable compositions for application to a fastener,particularly by the use of the said apparatus. In particular theinvention relates to adhesive compositions which are suitable for threadlocking or thread sealing applications. In general the present inventionrelates to a polymerisable composition for the sealing and locking ofengineering parts, particularly interfitting parts such as fasteners,more particularly threaded fasteners such as nuts, bolts, screws,threaded nails and the like, or parts such as pipe joints which may bethreaded or slip-fitted. Compositions of the invention may be used toassemble engineering parts where close tolerances are designed betweenadjacent surfaces of the parts. The invention particularly relates topre-applied compositions.

2. Brief Description of Related Technology

It is known to provide an apparatus for applying material to fasteners,in particular, threaded fasteners. One of the problems which have beenassociated with conventional apparatus for applying a compositionincludes the problem of contact marks. Contact marks arise wherefasteners touch off each other during the coating process. If thecoating is not dry to touch then some of the coating may come off ontoanother fastener, leaving a mark where contact was made (on one or bothfasteners). Such marks are known as contact marks.

One of the reasons for eliminating contact mark problems includesimproving the appearance of the end product. In particular, it isdesirable that fasteners will have composition only where it is requiredand will not have small amounts of the composition on other parts of thefastener, which detract from the aesthetic appearance of the fasteners.

Having composition on undesired parts of the fastener can alsodeleteriously affect the handling of the fasteners by automated machines(for example, robotic machines such as robotic grippers and the like).Due to the continued automation of assembly lines and the like, it isdesirable that fasteners can be handled by automated machines, forexample, machines for placing the fastener in a fastening position,and/or fastening parts mechanically with the fasteners. Such automatedapparatus will normally be designed to grip the fastener at a part ofthe fastener which has not had composition applied. This is to ensurethat composition does not find its way onto the handling apparatus forthe fastener. However, if composition has made its way onto other partsof the fastener (as discussed above), then it tends to come off on thehandling apparatus, eventually causing problems with gripping offasteners. It may interfere with moving parts of at least that part ofthe apparatus which grips the fastener and the like. Other methods ofhandling fasteners include pneumatic lines (often referred to as“shoots”) which essentially are hollow tubes through which the fastenersare blown by compressed air pressure. The fasteners can clog up in thetubes if the interior of the tubes becomes soiled with composition dueto contact of the fastener with the tube (contact marks on the interiorof the tube). Accordingly it is desirable that any coating applied issubstantially dry to touch when being passed through such systems.

Certain forms of apparatus which have been provided for applyingcoatings to fasteners include a drying oven in the form of a hightemperature oven which is used to dry the composition. There areinefficiencies in the process, as the amount of energy required to drythe composition is high. Furthermore, batching the fasteners togetherfor drying in the oven can lead to contact marks, as discussed above.Evaporation of water and/or solvent from a composition by heating maycreate contaminated extracted air which is another potentialdisadvantage.

It is desirable, therefore, to provide a handling mechanism that cancarry components through both the coating and drying processes to createa dry-to-touch composition applied to the fastener without creating anopportunity for contact marks to be formed by touching (e.g. bycollision) of fasteners. It is also desirable to provide a compactapparatus for application of curable composition. It is also desirableto provide an apparatus, which can have high throughput of components,which are coated, suitably in a compact arrangement.

One such handling apparatus is described in U.S. Pat. No. 6,027,568(Wallace et al). Wallace et al. describe an apparatus and method forproviding a masking, insulating and/lubricating barrier coating on aportion of threads of fasteners. The apparatus employs applicator guns,which fire a jet of composition onto the fasteners. The fasteners areconveyed along the apparatus by a conveyor and are delivered to an ovenwhere they are dried. Accordingly, it is likely that contact marks wouldbe formed in batching of the fasteners for drying in an oven. Thecompositions applied are not curable.

UK Patent Application No. GB 2 255 781 (Reactive Industries, Inc.)describes a composition which is UV-curable and which is applied tofasteners by an apparatus. The apparatus includes a conveyor having twospaced apart belts for conveying fasteners from a loading station pastapplicators and a heating station to a UV station. The fasteners arecaught between the two belts with two opposing sides at the head of thefastener resting on the top of the belts and the stem of the fastenerdepending vertically downwards in which position the fasteners are heldthroughout the processing steps.

UK Patent Application No. GB 2 255 781 (Reactive Industries, Inc.)already mentioned above describes a composition comprising ahardener-containing component which includes (a) a hardener capable ofpolymerising a resin, e.g., an epoxy resin; (b) a UV curablefilm-forming compound comprising a dimethacrylate; and (c) aphotoinitiator compound capable upon exposure to UV light of curing (b)to form an integral, thin continuous, dry, substantially pin-hole free,flexible, non-tacky outer protective skin. The hardener containingcomponent is preferably fluid and microencapsulated and can be used inan adhesive system additionally comprising a resin-containing componentwhich includes (1) a resin, e.g., an uncured epoxy resin which ispolymerisable by the hardener component, (2) a UV-curable film-formingcompound, e.g., a dimethacrylate; and (3) a photoinitiator capable uponexposure to UV light of curing the film-forming compound (2) to form anintegral non-tacky outer protective skin. The resin component may bemicro-encapsulated. In this system, also, the UV curing forms only anouter protective skin and the components for the second polymerizationare free to move beneath the skin or, in the event of rupture of theskin, to escape from it. The film-forming compounds used are monomers,particularly dimethacrylate monomers, and there is no suggestion of useof oligomers. The rheology of the composition is not discussed and, inparticular, the use of a thickener is not mentioned.

Compositions which are suitable for use in threadlocking applicationsare known. Such compositions find use in many applications. In generalthe compositions are used as described above to lock interengagingthreads together. The composition is generally placed on one or both ofcomponents which have reciprocal interengaging screw threads. When thecomponents are screwed together using the screw threads the compositionacts to lock the threads in the desired interengaged position.

In general the applications in which compositions of the presentinvention are used include any application where it is desired to lockscrewthreads together so that the components which are screwed togetherdo not become disengaged unintentionally, for example because ofvibrational or other forces. Such applications include use in theconstruction of automobiles etc.

Compositions have been used which must be applied at the time ofthreading one component into another, as the compositions remainsubstantially liquid before cure. Such compositions includeanaerobically curable compositions.

A pre-applied composition is described in U.S. Pat. No. 4,059,136, wheretwo physically separated deposits are applied to the threaded part. Acover coating is then applied over the deposits.

European Patent No. 0 077 659 (Thompson) describes a pre-appliedpolymerisable fluid for sealing and locking engineering parts. Thecomposition has two mechanisms for curing and two curing reactions takeplace. The first mechanism is a UV light cure. An opacifier is dispersedin the fluid so that the fluid becomes substantially opaque toradiation. After the fluid is applied to the component it is exposed toUV radiation whereupon a coating is formed, creating a surface layerwhich is a dry, tack-free crust. The subcutaneous fluid is unaffected bythe radiation and remains in a generally liquid state. When thecomponent is threaded into another the surface layer breaks and thesecond polymerisation (such as a free radical addition polymerization )is initiated and the second cure reaction takes place. The secondpolymerisation mechanism acts to lock the threads together.

In Thompson, only a skin is formed in the first polymerization and theremainder of the composition remains fluid below the skin. There is arisk therefore that during handling of the coated engineering parts theskin may be disrupted and the fluid composition may leak out.

European Patent No. 0 548 369 (Usami) describes a pre-applied adhesivecomposition for application to the threaded contact faces of a screwmember such as a screw. The composition comprises a photo-hardeningbinder in which a secondary curable composition is dispersed. Thesecondary curable composition includes microencapsulated reactivemonomer/activator/initiator. Exemplified compositions include thosecontaining (i) microencapsulated bisphenol A dimethacrylate and aradical generator; (ii) microencapsulated bisphenol A dimethacrylate andDMPT; and (iii) Three Bond product no. 3057D. The only information givenabout the product 3057D is that it is a UV-hardening acrylic resincontaining a photoinitiator. Other similar compositions are disclosed inthe other “Embodiments” described. In two “Embodiments” bisphenol Aepoxy resin is encapsulated. In one of these “Embodiments”, themicroencapsules enclosing bisphenol A epoxy resin are used with ThreeBond product no. 3057D, salicyclic acid derivative and aromatic diamine.The present applicants have not been able to obtain a sample of ThreeBond product 3057D and therefore have no information about the acrylicresin contained in it. In the other “Embodiment”, the microcapsulesenclosing bisphenol A epoxy resin are used with dialkylamino-acrylamideand a photoinitiator (DAROCURE 1173). There is a general indication inthe description that a filler may be added but no filler is used in the“Embodiments”. There is no suggestion of using a thickener, nor is thereany enabling teaching about the acrylic resin. So far as the presentapplicants are aware, no product has been commercialised under theEuropean Patent No. EP 0 548 369.

Notwithstanding the various compositions that have been provided it isdesirable to provide an alternative composition which is suitable foruse in thread sealing/thread locking applications. It is desirable thatsuch compositions are suitable for pre-application to threaded articles,for example to bolts, for later use. It is desired that the compositioncan be applied to form a dry-to-touch product on the threaded article.It is also desirable that the composition can be later activated to lockthreaded articles together with desirable properties of the bond formedbetween the threaded articles. To achieve s this the composition must bestorage stable before application and then remain stable for subsequentuse.

SUMMARY OF THE INVENTION

The present invention defines an apparatus and system for theapplication to a fastener of a composition curable by irradiation.

Accordingly, the present invention provides an apparatus for theapplication of an at least two-stage curable composition to a fastenercomprising:

-   -   (i) a conveyor for conveying fasteners to an application        station;    -   (ii) an application station comprising an applicator from which        the composition is dispensed, the conveyor for rotating at least        part of the fasteners past the applicator for application of        composition to the fasteners;    -   (iii) a conveyor for conveying the fasteners to an irradiation        station and arranged to rotate the fasteners for irradiation        thereof; and    -   (iv) an irradiation station for curing the composition applied        to each fastener.

The apparatus of the present invention is able to handle and coatvarious types of threaded parts, in particular, male threaded parts. Theflexibility of the apparatus to coat large numbers of different parts isquite advantageous. The end-users of the parts may require an approvalprocedure for each type of part they use. Accordingly, if the parts arecoated by different procedures, a different approval procedure may berequired. This is not so with the present invention, where the sameapparatus can handle different sizes of fasteners.

The apparatus of the invention is suited to high production speed, forexample, greater than 16,000 pieces per hour. The apparatus may be quitecompact, for example, no longer than 2 metres in length. For exampletypical dimensions including a feeding station are 2 m×2 m×1.5 m(height×length×width). This reduces installation and user spacerequired. The apparatus is also relatively portable, being quite easilymoved from one location to another.

The conveyor for conveying fasteners to an application station may bethe same conveyor as the conveyor for conveying the fasteners to anirradiation station. Desirably however they are separate (first andsecond) conveyors (conveyors which can run at different speeds forapplication and curing). In particular it is desirable that theapparatus comprises a first conveyor for conveying fasteners to anapplication station, and for rotating at least part of the fastenerspast the application station for application of composition to thefasteners. Suitably the first conveyor rotates the fasteners and conveysat least part of the rotating fasteners past the application station.The second conveyor can then be used to convey the fasteners toirradiation station. While most of the discussion of the presentinvention refers to the presence of first and second conveyors it willbe appreciated that the features of the first and second conveyors maybe applied, as appropriate, to a single conveyor apparatus.

In one desirable arrangement the apparatus further comprises a fastenerfeeder for feeding fasteners one by one to a first conveyor. This allowsfor timely and orderly feeding of fasteners to the first conveyor. Manyconveyors are of the movable support type, i.e., of the type thatsupport the material they carry. One example is a flat rubber belt whichcan carry product on its upper surface. Such conveyors do not normallycontinuously rotate (or roll) the material they carry. Conveyors whichcontinuously rotate (or roll) the products they handle are desired foruse in the present invention.

It has been found by the present inventors that it is desirable toadjust the temperature of the articles to which the composition is to beapplied prior to the application thereof. Accordingly it is desired toinclude temperature adjustment means for adjusting the temperature ofthe articles to which composition is to be applied.

Depending on the product in question it may be necessary to cool thearticles (for example if for any reason (such as ambient conditions)they are too hot (which for example will make applied composition lessviscous than desired or hot enough to deleteriously affect the stabilityof the composition) they may be cooled. If they are too cold thecomposition may not move well into the wells between threads (forexample due to increased viscosity).

Where it is desired to heat the articles one could therefore batch heatthe articles (for example in an oven) and later supply them to anapparatus according to the invention for application of composition.

However it is desirable to heat the articles in an inline process forexample before they reach, while they are passing through, or after theyexit the fastener feeder. In any event it is desirable to have thearticles heated before they reach the (first) conveyor.

Where pre-heating of the articles is desired hot air may be used to heatthem. For example an inline hot air blower may be employed. One usefulpiece if equipment includes any hot air blower which can heat air andwhich is arranged to deliver a strong focussed blast of hot air asappropriate to achieve the desired temperature.

Conversely for cooling, batch cooling can be employed but again it isdesirable to employ an inline cooling arrangement analogous to thatdescribed above for heating. In particular an air blower may also beemployed. An air blower with a suitable range of temperatures for theexpelled air may be employed to heat or cool as appropriate. Desirablythe articles are at a temperature in the range from about 30° C. toabout 60° C. such as about 35° C. to about 50° C. for example from about40° C. to about 45° C.

Pre-setting the temperature of the articles in this way makes thetemperature of the article independent from ambient temperature.

The composition should have at least two-stages of cure. The curablecomposition having a first cure stage which is activatable byirradiation so as to fix the composition to a fastener, and a secondcure stage which is curable to secure the fastener in a fasteningposition. The irradiation will normally cure the first stage cure of thecomposition.

The first conveyor desirably extends from the fastener feeder throughthe application station. The first conveyor may be arranged forconveying the fasteners in a manner so that the fasteners are arrangedon the conveyor in a configuration each spaced apart from the next, fromthe feeder to the application station (and suitably through theapplication station).

In particular it is desirable that the applicator comprises a surfaceonto which the product is dispensed. In one construction the fastenersare rolled across said surface by the first conveyor. Desirably, theapplicator is provided in the form of a coating block. The coating blockwill have a surface across which the fasteners are rolled or such like.In particular, it is desirable that at least one dimension of theapplicator may be altered (the contact made with the fastener can bevaried). This allows the application of different widths of product tothe fasteners. In particular, the applicator may have a contact portionfor contacting composition to the fastener with a width corresponding tothe width of a continuous coating layer of product that is desired toapply to the fasteners. In this respect a sufficient amount of productshould be provided in the spaces (pitches or wells) between threads inthe case that the fastener is a threaded one. A continuous coating layerof product in this respect refers to sufficient product within thespaces between threads of a threaded fastener. A certain amount ofproduct may find its way onto the threads themselves. However it isdesirable that the product does not completely fill or over fill thespaces between threads.

The width of the applicator can be varied to achieve differently sizedcoating layers of product about the fastener (usually confined to aportion of the fastener). Product will normally be continuous bothcircumferentially about the fastener and longitudinally along thefastener. It will be appreciated by those skilled in the art that in anarrangement where the fasteners are rolled across an applicator (with acontact portion for example with an application surface thereon) withcomposition thereon, a coating layer of product will be appliedcircumferentially about the fastener.

In one embodiment, the applicator surface is adjustable for applicationof different extents (coating layers) of product to fasteners. Inanother embodiment, the component on which an applicator surface isformed, for example, a coating block, is an interchangeable part, sothat different applicator surfaces (coating blocks) are mountable on theapparatus for use. Again this allows different threaded parts to beprocessed by the apparatus with a minimum of equipment alteration.

Furthermore it is also desirable to have a temperature control on theapplicator. In particular it may be desirable to heat or cool theapplicator surface. The temperature of the applicator in turn imparts adesired temperature to the composition which is applied from it. Inparticular it is useful to control the applicator temperature inconjunction with controlling the temperature of the articles to whichthe composition is to be applied. Again this makes the application ofthe composition independent from ambient temperatures. All heatingand/or cooling means may be controlled by a PLC (programmable logiccontroller) or PID (proportional integral differential) controller.Temperature may be monitored as appropriate for example by employing asuitable thermocouple.

In particular it is desired to maintain a temperature differentialbetween the bolts and the applicator. It has been found that it isdesirable to maintain a temperature difference of from about 10° C. toabout 20° C., such as about 15° C. between the applicator and thearticles. In particular it is desirable that the articles to which thecomposition is to be applied are higher in temperature than theapplicator. It has been found that the colder the articles are thegreater the thickness of product applied. However with cold (roomtemperature, 15° C. to 25° C.) articles and a non-heated applicator theamount of product which is applied (the coating or product layer) may betoo great and may cause the composition applied to overfill the pitchesbetween threads. (The product “humps” over the threads see for exampleFIG. 7A.) In particular it is desired that the composition betweenthreads forms a concave meniscus shape (see FIG. 7B) so that thecomposition to the centre of the pitch is at a lower level than thatthat at the threads. In this way the coating efficiency and coatingweight are balanced. The coating weight will be the minimum required toreduce peel-off and wastage. A coated article will be substantiallycompletely covered over the entire target (circumferential) area with athin even coating. It was found that by employing temperature as acontrol on coating weights works well. Suitably the applicator is at atemperature in the range of 28° C. to 35° C. such as about 30° C.

In the case where the applicator comprises a coating block it isdesirable that the coating block is temperature controlled for exampleby placing heating and/or cooling means in the coating block. Theheating means may be a heating element or cooling element or may beheated or cooled by circulated fluid such as water.

The second conveyor desirably extends through the irradiation station.The second conveyor may be arranged for conveying the fasteners in amanner so that the fasteners are arranged on the conveyor in aconfiguration each spaced apart from the next In particular the secondconveyor is used to convey the fasteners through the irradiationstation.

The fasteners need not be conveyed or otherwise moved between the firstand second conveyors. For example the momentum of a fastener exiting thefirst conveyer may be sufficient to carry the fastener to the secondconveyor where it is picked up by motion of the second conveyor. Largerfasteners (i.e., those with greater momentum) in particular may betransferred (travel) between conveyors in this way.

In one embodiment it is desirable that the apparatus further comprises atransfer station for transferring the fasteners (from the firstconveyor) to the second conveyor. The transfer station may comprise a(short) conveyor which acts to convey the fasteners between the (end ofthe) first and the (start of the) second conveyors. This is particularlyuseful for smaller fasteners.

In one compact arrangement it is desirable that the total length of thefirst and second conveyors is reduced. This may be achieved by at leastpartial overlap of the conveyors. In one arrangement the total distancefrom a fastener receiving end of the first conveyor to a fastenerexiting end of the second conveyor measured in a horizontal plane (inthe operating position of the apparatus) may be up to 50% less that thetotal combined length of the first and second conveyors.

One of the advantages in the provision of first and second conveyors isthat the speed of each conveyor to be selected may be accomplishedindependently from the other. In particular the speed of the firstconveyor (measured as the travelling speed of a fastener) issubstantially faster than the speed of the second conveyor. It is alsodesirable that the first conveyor is arranged to convey the fastenerswith a substantially greater lateral distance between the fasteners. Inone arrangement of the invention the transfer of the fasteners from thefirst to the second conveyor may result in the fasteners being groupedtogether a smaller distance apart but in any case it is described thatthe fasteners are a shorter distance apart on the second conveyor. Forexample the distance between fasteners conveying by the first conveyoris desirably 4 to 10 times the width of the fastener. (If the fastenerhas a head then desirably the spacing is 4 to 6 times the width of thehead.) In the second conveyor the spacing is desirably 1.5 to 2.5 timesthe width of the fastener (or of the fastener head). The speed of thefirst conveyor is typically 2 to 3 times the speed of the secondconveyor. Typical speeds are 0.1 to 0.5 m/s for example 0.22 m/s for thefirst conveyor or typically has a speed of 0.05 to 0.2 m/s such as 0.09m/s. The reduction of speed through the second conveyor and the closertogether fasteners allow for a substantial reduction in the overalllength of the first and second conveyors, thus reducing the overalllength of the apparatus.

In particular at least one and desirably each of the first and secondconveyors of the invention comprise at least one (endless) belt which isarranged to run substantially constantly spaced apart from a rail (it isalso possible to use an (endless) chain or such like but a belt ispreferred). The belt and the rail are suitably arranged to grip thefasteners between them so that motion of the belt (in at least onedirection) causes the fasteners to roll along the rail. In this way thefasteners can be rotated and moved along at the same time. At least onerail may run from the applicator station through to the irradiationstation.

Desirably the fastener is a threaded fastener such as a bolt, screw,plug, stud, fittings and the like. Typically the threads of the fastenerengage with reciprocal threads of a receiver for the fastener forexample a threaded bore or nut and the composition (in particular stagetwo thereof) is activated on screw thread engagement of the fastener toact as a threadlocking composition to lock the threads together or as athread sealant composition to provide a seal about (the threads of) thefastener. Threadlocking compositions are well known to those skilled inthe art, desirably both the threadlocking and thread sealingcompositions will have the two stage cure system described above. Inparticular it is desirable that the composition applied by the apparatusof the invention is a one-part composition (having a two-stage cure).

Desirably, the fasteners are conveyed by at least the first conveyor(and desirably the second conveyor also) so that they are substantiallyhorizontal. The fasteners will normally be threaded. They may or may nothave a head. The fasteners may or may not be ferromagnetic (e.g., steel,brass or stainless steel).

In one particularly desirable arrangement, the fastener comprises afirst end and a second end with a stem portion between the first andsecond ends. Desirably, the apparatus comprises a rail for supportingthe stem of the fastener at least one location thereon (at least whilethe fastener is being conveyed by the first conveyor). Desirably, a railis provided also, for supporting the fastener when it is conveyed by thesecond conveyor.

In one particularly desirable arrangement, two spaced apart rails areprovided to support the fastener at least two positions thereon. It isdesirable that neither of said two positions coincides with the part ofthe fastener which has had, or is for, application of composition atleast until the fastener is sufficiently far through the apparatus sothat the composition is dry to touch.

The fasteners may typically be in the range from 5 mm up to 200 mm inlength. Such fasteners do not need a head for transportation or forguidance along the apparatus. The invention is particularly suitable foruse with threaded fasteners having a head portion and a stem portionthereon.

In one particularly desirable arrangement, suitably the rail or railsfor supporting the fastener are adjustable so that different sizes(lengths) of fasteners may be accommodated by the apparatus. Inparticular, where two rails are provided, it is desirable that they areadjustable relative to each other so that the spacing between the railsmay be varied as desired. Such rails are desirably of a narrow width,for example, between 1 mm and 5 mm in thickness. Desirably, two parallelrails are provided. Product may be applied to the portion of thefastener that is arranged to lie between the rails.

Desirably, the application station comprising a supply system forsupplying curable composition to the flat applicator surface. In oneembodiment, desirably the component on which the flat applicator surfaceis formed has one or more apertures defined therein which pass to andthrough the applicator surface so that the product may be providedthrough the apertures to the applicator surface.

Desirably, the conveyor comprises a belt of material, desirably flexiblematerial. In particular, it is desirable that the belt comprisesresiliently deformable material, and in one embodiment of the invention,comprises O ring material. An O ring is a closed loop of material wherethe cross section of the material making up the ring is substantiallycircular (O-shaped).

Desirably the supply system for supplying composition to the applicationstation contains a product supply, which is operated by volumetricsupply.

Alternatively or additionally the supply system for supplyingcomposition to the application station includes a time/pressure controlsystem such as an air-pressurised line which pushes product from aproduct reservoir along a conduit toward the applicator. In the casewhere both a time/pressure system and a volumetric system are employedit is desirable that the time/pressure system feeds product to thevolumetric control system, which in turn supplies the product to theapplicator station. Desirably, a control is provided for controlling therate of product supply.

It has been found that the inclusion of a volumetric system results in amuch more convenient system as a user of the system has no longer tocontinually adjust the supply of the product due to ambient changes suchas pressure/temperature change. In particular it is difficult with adirect feed to the applicator station from a time/pressure system tocontrol supply rate where the product to be supplied is viscous.

Accordingly the present invention also provides a feed supply system forsupplying a composition to the application station of an apparatus ofthe invention the system comprising:

-   -   (i) a volumetric supply pump for taking product from a product        supply and supplying the composition to the application station        in a volumetrically controlled fashion; and    -   (ii) a control for controlling the supply rate of the pump.

Mechanical handling of the product may cause the product to prematurelycure and thus deleteriously affect the composition and the apparatus.For example where the composition includes a microencapsulated componentany mechanical handling can cause shear forces which rupture themicrocapsules causing premature curing of the composition rendering itsubstandard perhaps to the point of being completely useless, and alsocontaminating the apparatus with the cured product. Neither of these isdesirable.

Surprisingly it has been found that an eccentric rotor pump can be usedas part of the feed supply system of the present invention, which ofcourse may in turn be used as part of the apparatus of the presentinvention.

Generally an eccentric rotor pump will include a rotor and a stator, therotor being a single helix shape and the stator being a double helixshape. In general the rotor and stator will together form a closedcavity along which the composition is pushed by relative rotation of therotor and the stator.

In conjunction with such a system it is desirable to calculate a desiredamount of product per fastener and set the fastener feed rate and theproduct supply rate. Once the fastener and the composition to beemployed have both been selected the feed supply can be calibrated sothat a desired amount of product can be provided to the fasteners in apredictive fashion. There will be no need for continual adjustment ofthe supply rate for pressure/temperature differences.

A conduit which takes the composition from the volumetric supply pump tothe applicator station is desirably both relatively short and rigid.Reducing the length and avoiding a flexible conduit (such as a flexiblehose) may allow better volumetric control to be achieved, as flexing ofthe conduit, particularly over relatively long lengths can be avoided.

With a product supply system such as described above the amount ofproduct to be supplied will (once a fastener type is selected forapplication of composition) depend on the rate at which the fastenersare throughput.

The applicator desirably has a spreading surface onto which thecomposition is dispensed. The spreading surface may or may not berecessed so that product is present below a surface of the applicatoracross which the fasteners are rolled.

The products coated by the apparatus of the present invention are dry totouch, and thus can be collected in batches (in contact with each other)without fear of contact marks developing on some of the components. Thepresent invention achieves substantially no contact marks on pieces,which have been processed by the apparatus of the present invention. Forexample, even with 16,000 pieces an hour being processed, very lowpercentages of these products would have to be rejected due to contactmarks. Contact marks would generally appear on less than 1% of thepieces and, in particular, less than 0.1% of pieces using the process ofthe invention. Markings on less than 0.035% of fasteners has beenachieved while 0.005% or less is possible (50 pieces in a million).

Desirably, the irradiation station comprises a UV light source forirradiating product with UV light. In such instances, it is desirablethat the first cure stage of the curable composition is activatable byUV light. Desirably, the UV light source is a high intensity lamp,typically having an output of 120 W/cm. The fastener may experience anintensity of 40 m/Wcm². Desirably the irradiation station comprises afocused radiation emitting source, such as for example a focused UVsource for example the light source may be housed in a reflectivehousing which focuses the UV light into a narrow coating layer. Forlarger bolts in particular the irradiation time is not so critical and alower intensity source may be used.

It will be appreciated by those skilled in the art, that the limit ofthe capacity of the apparatus of the present invention to carry articlesfor application of coating is limited by the smallest size of conveyorthat can convey the piece and leave sufficient of the fastenerunobstructed for application of a coating.

Desirably, the first conveyor and the application station are arrangedin-line.

The apparatus of the invention is used for application of an at leasttwo-stage curable composition. In another aspect this applicationrelates to a composition suitable for use with the apparatus.

The present invention provides in one aspect a curable compositionsuitable for use in threadlocking applications comprising:

-   -   (a) a (meth)acrylate functional monomer component;    -   (b) a (meth)acrylate functional oligomer component;    -   (c) a photoinitiator component;    -   (d) a thickener component;    -   (e) an amine component; and    -   (f) an encapsulated epoxy resin component.        Optionally, additionally the inventive composition may include        an acrylamide component, which may be present within any one or        a number of the components (a) to (f) above or may be present        otherwise. In particular, an acrylamide, such as        N,N-dimethylacrylamide, may suitably be used.

The inventive compositions have desirable properties, such as forming adry to touch (tack-free) product following application to a threadedcomponent in a liquid state and subsequent UV cure to its dry state. UVcure of compositions of the invention occurs right through the depth ofthe product on the threaded article and the cured product is not onlydry to touch but is substantially dry (substantially solid) throughoutthe entire matrix it forms. Within that matrix the components for thesecond cure mechanism are held.

In particular, compositions of the invention have a first and secondcure mechanisms so that first and second cure reactions take place. In afirst cure mechanism/reaction the composition is UV hardenable to form asolid binder matrix within which components of the secondary curemechanism are held. In particular components (a)-(d) form the UVhardenable binding matrix. Components (e) and component (f) (amine andencapsulated epoxy) are the subject of a second cure mechanism/reaction.These latter components are held within the binder matrix once a UV curehas been carried out.

Compositions of the invention should not contain any opacifier componentwhich renders the composition substantially opaque to cure-initiatingradiation. Cf. Thompson.

In a particular aspect the present invention provides a curablecomposition for application to a threaded article, comprising adispersion of:

-   (i) components of a first cure mechanism comprising:    -   (a) a (meth)acrylate functional monomer component;    -   (b) a (meth)acrylate functional oligomer component; and    -   (c) a photoinitiator component;-   (ii) components of a second cure mechanism comprising:    -   (e) an amine component; and    -   (f) an encapsulated epoxy resin component; together with-   (iii) a thickener component suitable to impart sufficient viscocity    to the uncured composition to maintain the dispersion of the other    components in the composition; where the photoinitiator component is    suitable upon irradiation of the composition to achieve a first cure    through the depth of the composition applied to a threaded article    so that a binder matrix is formed with the components of the second    cure mechanism dispersed through the matrix.

It is important, in particular, that microcapsules containing the epoxyresin remain dispersed through the composition before and after thefirst cure.

The viscocity of the composition containing components (a) to (e) butexcluding component (f) is suitably within the range of 300 mPas to3,000 mPas when measured by Haake Roto Visco 1, C60/1° Cone, shearrate=244 s⁻¹.

The second cure mechanism is subsequently activated by rupture of themicrocapsules within the binder resulting in reaction of amine with theepoxy component which is released from the microcapsules. The secondcure mechanism then acts to lock the threads together. Good bondstrengths are achieved as measured by the torque required to unlockthreaded articles locked to each other by compositions of the inventionfrom each other.

Apart from the requirements for suitable cure properties of the firstand second cure mechanisms, there are a number of other properties thecomposition should have in order to be particularly useful as a threadlocking or thread sealing composition. One such property relates to theUV curable portion of the composition. That portion of the compositionshould cure to form a flexible but dry solid on the threaded article towhich is applied. Furthermore, that portion of the composition shouldalso act as a suitable matrix for the dispersion of the microcapsulesand the amine. It has been found that in compositions of the presentinvention the UV curable part of the composition cures to form a dryproduct with desired flexibility. Furthermore it acts as an excellentmatrix within which the microcapsules and the amine can be dispersed.

Flexibility of the UV cure product is desirable so as to allow for thecured material to be carried with the threads into contact with thereciprocal threads with which they will be engaged. If the product istoo brittle it will not travel well with the screw threads and would beinclined to be sheared or pared off by the screw thread action at thepoint of entry of one set of threads with the other and thus not reachthe desired location further down the screw threads. Bond strengthswould be poor. If the material is too soft then it may not besufficiently robust for handling and may be removed accidentally, suchas in automated equipment handling. An amount of rupture of themicrocapsules might also result from handling as the microcapsules maynot be so well protected from damage during handling. In general bondstrengths would be poor if epoxy material had (leaked from themicrocapsules and) cured prior to the screw threading action. Thecompositions of the present invention demonstrate the required amount offlexibility without being too brittle in nature.

In particular it is desirable that the component (a) comprises anacrylate monomer. Acrylate monomers have been found to be particularlysuitable with the compositions of the present invention. Any mono-, di-,or tri-functional acrylate may be employed.

Specific examples of methacrylate functional monomers which may beemployed in the present invention include: hydroxy ethylmethacrylate,lauryl methacrylate, isobutyl methacrylate, hydroxy propyl methacrylate,isobornyl methacrylate and methyl methacrylate.

Specific examples of acrylate functional monomers which may be employedin the present invention include: ethoxylated (3) phenol monoacrylatesuch as Photomer 4039 from Cognis; ethoxyethoxyethyl acrylate; bisphenolA epoxy diacrylate; isobornyl acrylate; acrylated adhesion monomer suchas Craynor 131B from Cray Valley, a diacrylate such as Photomer 4127Ffrom Cognis; 1,6-hexanediol diacrylate; acrylated polyester adhesionpromoter such as Craynor 704 from Cray Valley; and methylacrylamide;acidic mono and tri-acrylates such as SR9050, SR9051 from Sartomer. Itis particularly desirable to include an acrylamide, preferablyN,N-dimethylacrylamide, which has been found to contribute to the curestrength of the product.

Desirably component (a) comprises a combination of acrylate functionalmonomers. In particular it is desirable that component (a) comprises acombination of mono- and di- functional acrylate. The cure product ofcompositions of the invention including a combination of monomers hasbeen found to have desirable properties including suitable adhesionproperties of the binder to keep the cured product on the article towhich it is applied and UV cured.

Suitable combinations of acrylates include a first ingredient selectedfrom: Ethoxylated (3) phenol monoacrylate such as Photomer 4039 fromCognis; ethoxyethoxyethyl acrylate; bisphenol A epoxy diacrylate;isobornyl acrylate; diacrylate such as Photomer 4127F from Cognis; and1,6-hexanediol diacrylate; and a second ingredient selected from:

N,N-dimethylacrylamide; and/or an acrylate polyester adhesion promotersuch as Craynor 131B or Craynor 704 from Cray Valley, methylacrylamide;acidic mono and tri-acrylates such as SR9050, SR9051 from Sartomer.

It has been found that it is desirable to select component (b) fromamong acrylate functional oligomers. The nature of an oligomer is wellunderstood by those skilled in the art. Again (particularly incombination with an acrylate monomer as component (a)) selecting thismaterial in this way gives desirable cure properties to the UV curablebinding material and contributes to the viscosity which is desirable formaintaining dispersion of the components in the composition. From amongsuitable acrylate functional oligomers it has been found that epoxyacrylate and urethane acrylate functional oligomers result in desirableproperties.

Specific examples of acrylate functional oligomers which may be employedin the present invention include those given below as epoxy acrylate orurethane acrylate materials and additionally polyether acrylate such asGenomer 3497 from Cray Valley.

Suitable epoxy acrylate materials include:

bisphenol A epoxy acrylate such as Craynor 104 from Cray Valley orCraynor 115 (Lower viscosity version of Craynor 104) from Cray Valley;modified tetrafunctional epoxy acrylate such as Craynor 190 from CrayValley.

Suitable urethane acrylate materials include aliphatic urethanematerials and also resins prepared in accordance with InternationalPatent Publication No. WO 98/31655 and U.S. Pat. No. 4,295,909 (Baccei);Flex Resin II and Acryflex from Henkel Loctite; Genomer 1122 from RohmAG; Ebecryl 230,270, 3500, 8402 and 4842 from UCB/Radcure; and Craynor965 from Cray Valley.

More particularly it has been found that where component (b) comprises acombination of epoxy acrylate and urethane acrylate functionaloligomers, cure products with the types of desirable properties set outabove are achieved.

As with the other components of compositions of the present invention itis desirable that component (c), the photoinitiator component, may bechosen to have specific properties.

The photoinitiator can be selected from among: phosphine oxides;hydroxyketones and moropholino compounds.

Suitable photoinitiators include:

diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide; 1-hydroxycyclohexylphenyl ketone; bis (2,4,6-trimethylbenzoyl)-phenylphosphine oxide suchas Irgacure 819 from BASF; 2,2′-dimethoxy-2-phenylacetophenone;2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone;2-methyl-1-(4(methylthio)phenyl)-2-moropholino-1-propane; bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl pentyl phosphine oxide; and1-hydroxy-cyclohexyl-phenyl-ketone (a blend of 25:75 of the latter twocomponents may be employed).

For example it is important to achieve good cure through volume (CTV).It has been found that selection of certain photoinitiators can improvethe CTV achieved. Therefore it is desirable that component (c) comprisesa component which enhances depth of cure. Without such a depth of curethe product may remain partially uncured on a threaded article to whichit is applied, which is undesirable. Suitable photoinitiators whichachieve this effect include photoinitiators with phosphine oxidefunctionality such as diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide;bis (2,4,6-trimethylbenzoyl)-phenylphosphine oxide and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl pentyl phosphine oxide.Photoinitiators with phosphine oxide functionality have also been foundnot to impart a yellow colour which may be imparted by otherphotoinitiators. Such photoinitiators can be considered “non-yellowing”.

Another important factor in achieving a dry (tack-free) product isachieving sufficient surface cure of the composition. Without sufficientsurface cure of the composition it will remain wet/tacky to touch. Ithas been found that selection of certain photoinitiators can improve thesurface cure achieved. Therefore it is desirable that component (c), thephotoinitiator component, includes a component which enhances surfacecure is also desirable to achieve a suitable end product. Suitablephotoinitiators which achieve this effect include: hydroxy ketones,e.g., α-hydroxy ketones. Specific photoinitiators that may be usedinclude: 1-hydroxycyclohexyl phenyl ketone;2,2′-dimethoxy-2-phenylacetophenone;2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone; and4-hydroxycyclohexyl phenyl ketone.

Utilising a combination of (i) a component which enhances depth of cure,and (ii) a component which enhances surface cure as a photoinitiator isparticularly useful. In this respect it has been found that utilising acombination of a photoinitiator with phosphine oxide functionality and aphotoinitiator with hydroxy ketone functionality is desirable. Typicalratios of use are 20:80 to 30:70 such as 25:75 respectively.

The thickener component also plays a part in the compositions of thepresent invention. In particular it is desirable to include a thickenercomponent to thicken the uncured formulation which is usually liquid.The thickening of the composition imparts sufficient viscosity to thecomposition so that it has the physical properties to allow and maintainthe dispersion of the other components in the composition, in particularprior to UV cure. In particular it is desirable that the microcapsulesremain dispersed throughout the composition. If the composition was notsufficiently viscous the settling out of components may occur. Thismight result in the first cure reaction not sufficiently curing thebinder composition throughout its mass. Secondly the components of thesecond cure mechanism, in particular the microencapsulated epoxycomponent, may become localised in one part of the composition (forexample at the bottom of a mass thereof) and when the UV cure takesplace the binder does not contain an even distribution of the componentsof the second cure mechanism. Accordingly, subsequent rupture of themicrocapsules and reaction thereof with the amine may not result in adesired bond strength between threaded components.

The thickener component [component (d)] may be selected from organicthickener materials such as waxes and polymeric thickeners and alsoinorganic thickener materials such as silica.

Suitable organic materials include:

polymethyl methacrylate (PMMA) granules; polyethylene materials;fluoropolymers including polytetrafluoroethylene (Teflon™) materials;nylon materials; and co-polymer materials such as methyl/n-butylmethacrylate copolymer. Any of the foregoing may be provided in powderform.

Gums such as xanthum gum (also polymeric) may be utilised also.

Silica has been found to be a very useful thickener component inaccordance with the present invention. It achieves the necessarythickening of the composition without interfering to any substantialextent with the first or second cure mechanisms.

Suitable silicas, such as fused silicas, may be untreated or treated soas to alter the chemical nature of their surface. Virtually anyreinforcing fused silica may be used.

Particularly desirable silicas have a low ion concentration and arerelatively small in particle size (e.g., on the order of about 12 μm,with a median of up to about 30 μm and as low as less than about 2 μm),such as the Silbond materials, commercially available under thetradename Aerosil 200, supplied by Degussa.

Other materials may be added as (inorganic) thickener components andinclude those constructed of or containing aluminum oxide, siliconnitride, aluminum nitride, silica-coated aluminum nitride and micronizedquartz, provided they are not basic in nature.

Desirably, component (e) may be a tertiary amine. Tertiary amines havein particular been found to have a suitable rate of cure were used incombination with the epoxy material released from the microencapsulatedepoxy materials of the present invention. Teritary amines are alsolikely to provide a better shelf life for compositions containingacrylate monomers than would be the case with primary or secondaryamines. Included within the scope of the invention are amines where thenitrogen atom forms part of a heterocyclic group such as a substitutedor unsubstituted pyridine group. Those tertiary amines which are usefulin the present invention include hindered tertiary amines. Of hinderedtertiary amines which are useful, the subgroup of hindered aromatictertiary amines are of note. Specific amines useful in the presentinvention include: 1,3-di(4-pyridyl)propane(dipyr); modified polyaminesuch as Ancamine K54 from Air Products; primary amine such as4,4′-diaminodicyclohexylmethane; secondary amine such as1,3-di-4-piperidylpropane; biaryl containing amine substituents such asKayahard A-A or Kayahard A-B from Nippon Kayaku. Dipyr is a veryeffective material in this respect. The subgroup of hindered tertiarybiaryl amines are of note.

Component (f), the epoxy material, which is microencapsulated includesmany common epoxy resins, such as those having monofunctionality andmultifunctionality (for example those having two or more epoxy groupsper molecule). Examples of such epoxy resins with monofunctionalityinclude C₄-C₂₈ alkyl glycidyl ethers; C₂-C₂₈ alkyl- and alkenyl-glycidylesters; C₁-C₂₈ alkyl- and mono-phenol glycidyl ethers. Examples of suchepoxy resins with multifunctionality include poly-phenol glycidylethers; cycloaliphatic epoxy resins; polyglycidyl ethers ofpyrocatechol, resorcinol, hydroquinone, 4,4′-dihydroxydiphenyl methane(or bisphenol F), 4,4′-dihydroxy-3,3′-dimethyldiphenyl methane,4,4′-dihydroxydiphenyl dimethyl methane (or bisphenol A),4,4′-dihydroxydiphenyl methyl methane, 4,4′-dihydroxydiphenylcyclohexane, 4,4′-dihydroxy-3,3′-dimethyldiphenyl propane,4,4′-dihydroxydiphenyl sulfone, and tris(4-hydroxyphyenyl)methane;polyglycidyl ethers of the chlorination and bromination products of theabove-mentioned diphenols; polyglycidyl ethers of novolacs; polyglycidylethers of diphenols obtained by esterifying ethers of diphenols obtainedby esterifying salts of an aromatic hydrocarboxylic acid with adihaloalkane or dihalogen dialkyl ether; polyglycidyl ethers ofpolyphenols obtained by condensing phenols and long-chain halogenparaffins containing at least two halogen atoms; phenol novolac epoxyresins; cresol novolac epoxy resins; and combinations thereof.

Among the commercially available epoxy resins suitable for use hereinare polyglycidyl derivatives of phenolic compounds, such as thoseavailable under the trade names EPON 828, EPON 1001, EPON 1009, and EPON1031, from Shell Chemical Co.; DER 331, DER 332, DER 334, and DER 542from Dow Chemical Co.; GY285 from Ciba Specialty Chemicals; and BREN-Sfrom Nippon Kayaku, Japan. Other suitable epoxy resins includepolyepoxides prepared from polyols and the like and polyglycidylderivatives of phenol-formaldehyde novolacs, the latter of which areavailable commercially under the trade names DEN 431, DEN 438, and DEN439 from Dow Chemical Company. Cresol analogs are also availablecommercially under the trade names ECN 1235, ECN 1273, and ECN 1299 fromCiba Specialty Chemicals. The cycloaliphatic epoxy resin, UCB CAT-002,available commercially from UCB, is desirable as well. SU-8 is abisphenol A-type epoxy novolac available from Shell Chemicals (formerly,Interez, Inc.). In addition, UVR-6105 and 6110 (each3,4-epoxycyclohexylmethyl-3,4epoxycyclohexane carboxylate) and UVR-6128[(bis-(3,4-epoxycyclohexyl)adipate], each available commercially fromUCB Chemicals, are desirable for use herein, with the latter beingparticularly desirable. And of course combinations of the differentepoxy resins are also desirable for use herein.

The capsule itself is desirably a double walled capsule. An example of adouble walled capsule is one including walls constructed of gelatinand/or polyoxymethylene urea (PMU).

Desirably the concentration of epoxy resin component within the capsuleis between 40 and 100%, more typically 50 to 80%, suitably 50 to 70% forexample 50 to 60% (weight/weight).

In any event to ensure good cure, particularly of the second curemechanism desirably the amount of epoxy which is introduced with themicrocapsules and which is not internally held in the microcapsulesprior to their rupture by screw threading is desirably less than about0.5% by weight of the total composition. Epoxy may be carried externallywith the microcapsules or may be released on premature rupture of themicrocapsules. This means that the second cure mechanism reaction willbe substantially unaffected.

It has been found that the mean diameter of the microcapsules isdesirably in the range of from about 100 μm to about 140 μm though itwill be appreciated that individual capsules may have a diameter welloutside these mean ranges. For example individual microcapsules can havea diameter in the range of from about 50 μm to 200 μm. Suitably the meandiameter is in the range from about 110 μm to about 130 μm. Typicallythe mean diameter will be about 120 μm.

A further component which is suitable for use in compositions of thepresent invention is a plasticiser component. While many plasticisercomponents may be utilised, it is desirable that the plasticiser is apolymeric one such as PMMA. Other plasticisers may also be included inthe inventive composition examples of which include those availablecommercially from Union Carbide, such as under the trade designationsTONE Polyol 301 and 310. Other suitable plasticiser components includeexpandable plastic such as those sold under the trade name EXPANCEL.According to information from the website http://www.expancel.com/,EXPANCEL is a registered trade-mark for microspheres which are smallspherical plastic particles. The microspheres consist of a polymer shellencapsulating a gas. When the gas inside the shell is heated, itincreases its pressure and the thermoplastic shell softens, resulting ina dramatic increase in the volume of the microspheres (by a factor of40). The specific material which can be used is DE 80 or DE 30. It isuseful that compositions of the present invention can have a colourimparted thereto. Usually, pigments can be added to the compositions ofthe present invention without any substantive interference in the firstor second cure mechanisms. It is useful to impart a colour tocompositions of the present invention, as the colour can be used as aproduct indicator in many ways, usually to allow for ease orrecognition, for example, to indicate a particular size of bolt or nut,the customer to whom the threaded article with the pre-applied productshould be delivered.

Suitable pigment components include coloured metal complexes for exampleFe and Co complexes. Specific examples include:

Rocket Red T-13 (organic pigment based on a thermoset resin matrixincluding an Fe complex material available from Dayglo Color Corp); alsoLaser Red 2 and Laser Red 3 with similar chemistry and available fromSterling;

Cobalt aluminate complexes such as the product PK5091 from Ferro B. V.and Comet Blue 3 from Swada (both Cobalt aluminate blue spinelmaterials);

V-9248 Blue (Cobalt chromite blue-green spinel from Ferro B. V.);

F-5686 Turquoise (Cobalt chromite blue-green spinel Co(Al,Cr)₂O₄:MgO:ZnOfrom Ferro B. V.).

In general Fe complexes impart a red colour whereas Co complexes imparta blue colour. It is unusual to be able to colour materials which are tobe cured by UV light with a blue pigment as a blue pigment normallyinterferes to a substantial extent with the cure process by absorbing UVlight.

Suitable amounts for the components of the UV binder part of thecomposition based on weight by weight percentage based on that part ofthe composition excluding the microencapsulate epoxy component (i.e.,the composition excluding the microcapsules being taken as 100% of theweight) may be selected independently of one another as follows:

(meth)acrylate functional monomer, 25 to 45% more typically 30 to 42%suitably 32 to 40% for example 33 to 38%;

(meth)acrylate finctional oligomer, 35 to 55% more typically 39 to 52%suitably 41 to 50% for example 43 to 48%;

photoinitiator, up to 15%; more typically 1 to 12% suitably 3 to 10% forexample 5 to 8%;

thickener, up to 14% more typically 1 to 11% suitably 2 to 9% forexample 4 to 7%; and

amine, 2 to 14% more typically 4 to 14% suitably 6 to 12% for example 8to 10%. Suitable combinations are disclosed above,

where component (a) comprises a combination of (meth)acrylate functionalmonomers: one of the monomers is typically present in the range of 15 to29%, more typically 17 to 27%, suitably 19 to 25%, for example 21 to23%, whilst a second monomer is typically present in the range of 7 to21%, more typically 9 to 19%, suitably 11 to 17%, for example 13 to 15%;

where component (b) comprises a combination of (meth)acrylate oligomers:one of the oligomers is typically present in the range of 22 to 38%,more typically 24 to 36%, suitably 26 to 34%, for example 28 to 32%,whilst a second oligomer is typically present in the range of 7 to 22%,more typically 9 to 20%, suitably 11 to 18%, for example 13 to 16%;

where component (c) comprises a combination of photoinitiators: one ofthe photoinitiators is typically present in the range of 0.2 to 9%, moretypically 0.4 to 7%, suitably 0.6 to 5%, for example 0.8 to 3%, whilst asecond photoinitiator is typically present in the range of 1 to 12%,more typically 2 to 10%, suitably 3 to 8%, for example 4 to 6%; and

where component (d) comprises a combination of thickeners: one of thethickeners is typically present in the range of 0.5 to 10%, moretypically 1 to 8%, suitably 2 to 6%, for example 3 to 4%, whilst asecond thickener is typically present in the range of 0.2 to 9%, moretypically 0.5 to 7%, suitably 0.7 to 5%, for example 0.9 to 3%.

As already stated ranges are based on weight by weight percentage basedon that part of the composition excluding the microencapsulate epoxycomponent (i.e., the composition excluding the microcapsules being takenas 100% of the weight).

In particular the compositions of the invention are generally made up bypreparing the UV curable binder portion thereof and the amine and thendispersing within that composition the required amount ofmicroencapsulated epoxy component. For convenience therefore we willrefer to the ratio of the “binder composition” or “acrylate portion” asthat part of the composition including all of the components other thanthe microcapsules and the “microcapsule portion” as referring to theamount of the microcapsules.

Generally the ratio of mixing by weight of the binder composition to themicrocapsule portion is 50-70:30-50. The ratio of each will be selectedso that the combined ratios add to 100.

Typically the plasticiser component will be present in an amount of lessthan 3% by weight of the total composition.

Typically the pigment may be present in an amount from about 0.1 toabout 0.5% by weight of the total composition, such as from about 0.2 toabout 0.4%, for example from about 0.25 to about 0.35%.

The inventive composition can be stored for use as either a one-part ora two-part composition. When formulated as a two-part composition, thefirst part of the composition may comprise;

-   -   (i) a (meth)acrylate functional monomer,    -   (ii) a (meth)acrylate functional oligomer,    -   (iii) a photoinitiator,    -   (iv) a thickener,    -   (v) an amine,        and optionally additionally one or both of;    -   (i) a plasticiser    -   (ii) a pigment component.        whilst the second part of the composition will usually comprise        the encapsulated epoxy resin.

A composition stored as a one-part composition has a shelf life of atleast one week. Whereas a composition stored as a two-part composition,the first part of the composition has a shelf life of at least 6 monthsat 5° C., and the second part has an indefinite shelf life. When thetwo-part composition is mixed prior to use, the resulting compositionhas a shelf life of at least one week.

Subsequent to the first stage cure of the composition, the chemistry ofthe composition can confer reduced “peel off” of the composition on athreaded bolt following the second stage cure, depending upon the designof the bolt/nut joint.

The invention extends to apparatus substantially as described hereinwith reference to and/or as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an apparatus according to thepresent invention;

FIG. 2 is a side elevation showing a more detailed construction of anapparatus of the present invention;

FIG. 3 is an end part sectional view of the apparatus of FIG. 2 (fromthe left end thereof);

FIG. 4 is an enlarged partial view similar to that of FIG. 3;

FIG. 5 shows a cross-sectional view of an eccentric rotor pump for usein a feed supply system/apparatus of the invention;

FIGS. 6A and 6B respectively show: applicator (coating block)temperature plotted against coating efficiency; and coating efficiencyplotted against (fastener) bolt temperature; and

FIGS. 7A and 7B show a picture of a bolt with composition appliedthereto; FIG. 7A showing an excess of applied product and FIG. 7Bshowing a desirable amount of applied product.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a schematic representation of an apparatus according thepresent invention. The apparatus is for the application to fasteners ofa curable composition. The two-stage composition is desirably a one-partcomposition having at least two cure stages. The advantage of using aone-part composition is that application of the composition can takeplace in one step. If the composition is a two-part composition thenapplication of the two-parts of the composition normally takes placeseparately as mixing of the two-parts of the composition will cause thecomposition to cure.

The apparatus 1 has a conveyor for conveying fasteners 2 to anapplication station which in the embodiment is a coating block 5. Afirst conveyor is provided which includes an endless belt 3 (in FIG. 1only part of the belt is shown), which conveys the fasteners or bolts tothe coating block 5. It will be noted that the endless belt 3 picks upthe fasteners 2 and conveys them through the application station. Theconveyor 3 extends through the application station (passing across thecoating block 5).

The coating block 5 is a component of the apparatus that is replaceableand different sizes of coating blocks can be used to achieve differentamounts of applied product on the fasteners. With reference to FIGS. 2-4also provided is a second conveyor in the form of an endless belt 8which is for conveying fasteners 2 to an irradiation station which inthe embodiment is a focused UV light assembly 10. In particular theassembly 10 has a UV emitting light 11 housed in a closed housing 12 (inFIG. 1 the housing is shown in part cut-away to show the internal UVlight). An elongate aperture 13 is formed in the base of the housing 12,which allows a narrow band of UV light to escape from the housing 12. Acover (such as a sliding cover) may be provided over the slot. Thenarrow band of UV light is arranged to be coincident with a coatinglayer of applied composition 9 on the fasteners.

The coating layer of applied composition 9 is achieved by rotating thefasteners across the coating block 5. In particular the coating block 5has a contact portion for contacting the composition with the fastener.The contact portion is provided in the form of an application surface 14(on coating block 5) onto which the two-stage curable composition isdispensed. In the embodiment shown, beads 6 of the (liquid) compositionare dispensed onto the application surface 14 from the underside of thecoating block 5. This may be achieved by providing apertures in thecoating block which open onto the application surface 14 and for exampleusing a conventional dispensing system such as an air-pressurised line55 which feeds product to an eccentric rotor pump 53 which in turnsupplies product to the coating block 5 (best seen from FIG. 4). Theapparatus 1 also has a rail 4 (see also FIGS. 3 and 4), which supportsthe fastener close to one end of the fastener (the end closest thehead). The fasteners 2 are gripped between the belt 3 and the rail 4sufficiently well so that movement of the belt 3 in the direction of thearrow 16 (left to right in the orientation shown in FIGS. 1 and 2)results in the bolt moving in the direction of the arrow 16 all thewhile rotating (rolling) as indicated by arrow 17.

In the embodiment the coating block 5 forms (part of) a second railwhich also supports the fastener 2. Movement of the belt 3 thus causesthe fasteners 2 to rotate across rail 4 and application surface 14 ofthe coating block causing each fastener to roll through the product 6thus creating a coating layer 9 of applied composition. It will beappreciated that rotation of the fastener is about a longitudinal axisthereof.

As shown in FIG. 3 the coating block is temperature controlled by atemperature control element 52 which can be used to raise and lower thetemperature of the coating block (in particular an applicator surfacethereof). The element 52 is located in a bore within the coating block.

The fasteners continue to rotate (again about a longitudinal axis) whilepassing under the irradiation assembly 10 (rotation being effected bythe second conveyor 8). The emitted UV light (radiation) from theassembly 10 is arranged to irradiate the coating layers 9 of product soas to cure the composition so that it is dry to touch. The apparatusfurther comprises a feed—in means (fastener feeder) 15 which will,together with the remainder of the apparatus, be described in moredetail with reference to FIGS. 2-4.

The apparatus of the invention sits on a support structure, which hasbeen labelled 20. The apparatus has a fastener feeder 15 for feedingfasteners one by one to the first conveyor belt tray. As seen in FIG. 2an air blower 51 is provided for blowing air of a temperature selectedfor the fasteners. In particular the air blower 51 is of the typeusually described as an air knife blower. The blower 51 is arranged toheat at least that portion of the fasteners to which the compositionwill be applied as they pass through the fastener feeder 15.

As can been seen from FIG. 2 the belt 3 runs in a series of pulleywheels 22 arranged in line. The belt 3 is driven by a motorised pulleywheel 23. An adjustable (tensioning) pulley wheel 24 is provided whichcan be used to tension the belt 3 as appropriate. All of the pulleywheels are supported on an adjustable support frame 21.

In particular an adjusting mechanism is provided which is operated byrotation of a hand wheel 25. In particular the relative distance betweenthe belt 3 and the support 20 can be adjusted to accommodate differentsizes of bolts. In particular the distance between the belt 3 and thesupport rail 4 (see FIGS. 1 and 3-4) can be adjusted so that differentsizes of fasteners can be accommodated between the belt and the supportrail 4. As described with reference to FIG. 1 the coating block 5 isalso provided for application of composition to at least a portion ofeach of the fasteners 2.

The belt 8 works in an analogous fashion running across pulley wheels 26and been driven by a motorised pulley wheel 27 and tensioned by afurther tensioning wheel 28. The belt 8 and its associated pulley wheels26-28 are all mounted on an adjustable support 30 which can be adjustedby turning handwheel 29 to alter the vertical distance between the belt8 and the guide rail 4 (and the second rail 31).

If the fasteners have sufficient momentum, no additional mechanism maybe needed to effect transfer of the fasteners from belt 3 to belt 8, asat least certain fasteners may continue to roll along between exitingfrom belt 3 and before being picked up by belt 8. However it isdesirable (especially for smaller fasteners) to provide a transfermechanism between the two belts.

In the embodiment shown in FIG. 2 the last pulley wheel 37 (last in thedirection left to right) and the first pulley wheel 33 (again first inthe same direction) have arranged between them a transfer belt 32. Thetransfer belt 32 does not run directly between pulley wheels 37 and 33.This is because belts 3 and 8 run at different speeds. It is onlynecessary that the transfer belt 32 is driven at one end and runs on a(free wheeling) separate pulley on the other. In the embodiment the belt32 turns with the aid of pulley wheel 37 while it free wheels on aseparate pulley wheel at its other end (proximate first pulley wheel 26,i.e., wheel 33). As best seen from FIG. 3 the pulley wheel 37 is doublegrooved having grooves 38 and 39 in which the belts 3 and 32respectively run. The transfer belt 32 ensures smooth transition ofsmaller pieces between the two larger belts 3 and 8.

As described with reference to FIG. 1 light assembly 10 is provided toshine UV light on the applied product as discussed.

It will be appreciated that the bolts are continually rotated on alongitudinal axis when passing through the machine. Furthermore thefasteners are in a generally horizontal position. This is advantageousas the light source can be placed above the fastener rather than alongside it or beneath it so that it is less likely that product would comeoff the fasteners 2 and land on the lamp assembly 10. Fasteners exitingthe apparatus have been labelled 34 for convenience.

FIGS. 3 and 4 show a more detailed view, which is part sectional. In theview of FIGS. 3 and 4 the fastener feeder 15 has been omitted for thepurposes of clarity. As can be seen clearly from these Figures thesupport 21 can be moved vertically relative to the rails 4 and 31 (whichin turn moves the pulley wheels 22-24 and 37 as described previously) byvirtue of an adjusting mechanism 40 which is operated by the rotation ofhandwheel 25. In the view shown in FIGS. 3-4 the rail 31 does not appearas the view has been taken where the coating block 5 forms part of thesecond rail.

It will be noted from FIGS. 3 and 4 that a guide is provided each sideof the fastener to keep the fastener on the rails 4,31 through theentire apparatus. In particular a first guide 43 and a second guide 44guide the fastener along its travel path. In particular the first guide43 is in the form of an abutment plate against which the head 45 of thefastener abuts. The second guide 44 is also in the form on abutmentplate against which the stem 46 of the fastener abuts. The guides 43,44maintain the fastener on its path by preventing any substantial movementof the fasteners transversely across the rails.

It will be noted that the spacing between the rail 4 the guide 43 issuch that they form stops on opposing sides of the head (i.e. arrangedto abut the top side and the underside of the head of the fastener) thuspreventing the fasteners from moving off line to any great extent (byrestricting movement of the head). The rail 4 and the guide 43 assist inpreventing the fasteners arranging themselves in a diagonal directionacross the rails.

All of support 21 and the pulleys belts etc. are supported by theadjustment mechanism 40 and movement thereof allows the relativevertical distance between the rails 4 and 31 and in particular the belt3 to be adjusted.

Six rods 41, 42, 47-50 (see FIG. 2) arranged substantially horizontallyand vertically spaced apart form part of an adjustment mechanism whichis arranged to allow for adjustment of the apparatus to accommodatedifferently sized fasteners 2 (in particular those of greater length).Only two of the rods 41 and 42 are shown in view of S FIG. 3. Inparticular a slide mechanism operates along rods 41, 42 to allowadjustment of the apparatus in an essentially horizontal direction. Inparticular a clamp or lock 35 can be released which allows for thesubstantially horizontal movement of support 21 and all of itsassociated components together with the coating block 5, (block 5 moveson support 36) rail 31 and guide 44 to be moved closer or further awayfrom the remainder of the apparatus (for example rail 4). This allowsfor in particular longer fasteners to be coated using the apparatus ofthe invention.

The rail 4 and the first guide 43 are adjustable relative to each otherso that the distance between them can be selected allowing for use ofthe apparatus with fasteners having differently sized heads.

An enlarged end view of part of the apparatus shown in FIG. 2 can beseen in FIG. 4. Additionally shown in FIG. 4 is a reservoir 54 whichtogether with an air-pressurised line feeds composition held in thereservoir to the eccentric rotor pump 53. The eccentric rotor pump isconnected directly to the coating block 5 by a rigid connection toreduce losses in control of the amount being dispensed by length and/orflexing of the conduit.

More detail of the eccentric rotor pump 53 is shown in FIG. 5, whichgives a cross-sectional view of a suitable pump. The eccentric rotorpump 53 has a pump housing 102 with a rotor 108, which is mounted on adriven assembly 107. The rotor is connected to helical pump elements105, which are arranged in a general double helix arrangement within astator 104. Driving of the rotor 108 also rotates elements 105 andcausing a pumping action toward the outlet end 110 of the pump 53.

The process is carried out as follows:

The fasteners are fed into the first conveyor by a fastener feeder;

The conveyor conveys the bolts across an applicator which appliesproduct to the bolts, the bolts are then transferred to a secondconveyor which runs at a different (slower) speed;

The second conveyor conveys the bolts past the UV light source forcuring of the product applied in the application station. By the timethe bolts leave the second conveyor (see for example the bolts labelled34 in FIG. 2) they are dry to touch.

EXAMPLES

Separate bolts having applied thereto (by an apparatus of the inventionas shown in the Figures) a composition according to Example 1 below areshown in FIGS. 7A and 7B. FIG. 7A shows a bolt having a greater thanoptimal amount of product thereon. As described above and as set out ingreater detail below, the amount of product on the bolt which is appliedby the apparatus can be controlled so as to provide a desirable(optimal) amount of product such as in FIG. 7B. One of the main controlsfor the amount of applied product picked up by an article from theapplicator is temperature. Working within a selected temperaturedifference range between the applicator temperature and the articletemperature will allow a person skilled in the art to apply product indesired amounts such as is shown in FIG. 7B.

Coating Efficiency Tests Effect of Bolt and Coating Block Temperatures

This test examined (a) (article) bolt temperature and (b) (applicator)coating block temperature effects on the coating efficiency. The testtrials were carried out utilising an apparatus as shown in the drawingsand utilising a composition as set out in Example 1 below.

(a) Bolt Temperature Effects

Description:

To examine how changes in bolt temperature affect the coatingefficiency, the following settings were kept constant (on the apparatusas shown in the drawings—FIGS. 2-4): bolt feed rate, coating blocktemperature (30° C.) (conveyor in the applicator station) belt speed andpump speed.

Bolts were preheated to each of temperatures 35° C., 45° C. and 55° C.Samples from each temperature were run through the coating machine andcoating weight was calculated for each temperature by weighing a numberof samples from each run.

Product not coated onto the bolt was wasted over either the side or theend of the coating bar. The coating efficiency (%) is calculated asfollows: (Amount of product coated onto the bolt/amount of productpumped on to the coating bar per bolt)×100.

Results

FIG. 6A shows the coating efficiency with varying bolt temperature. Morespecifically, FIG. 6A shows that an increase in temperature of 20° C.gives a decrease in coating efficiency of 8%, and that preheating boltsto a temperature in the range of 30-40° may give an optimal coatingefficiency. Using pre-heated bolts also was observed to provide ahomogenous coating layer.

(b) Coating Block Temperature Effects

Description:

To examine coating block temperature effects the bolt temperature wasset to 40° C., and the coating bar was run with the followingtemperatures 25.6° C., 27.5° C., 30° C., 32.5° C. 35° C. The rest of thesettings were kept as before. The following graph shows average amountof product picked up per bolt with varying bar temperature.

Results:

FIG. 6B shows the coating efficiency with varying coating blocktemperature (coating block temperature controlled as described above).In this case we see that by raising the coating block (bar) temperaturefrom 26° C. to 35° C. increases the coating efficiency by 7.5%.

As bolt temperature increases, coating weight and coating efficiencydecreases. As the temperature of the coating block increases, coatingweight and coating efficiency also increase. As all runs produced goodquality coatings (as exemplified in FIG. 7B), both bolt and coatingblock temperature can be used to control the coating efficiency of thesystem.

UV Acrylate/Epoxy Threadlocking Compositions

A threadlocking formulation according to the invention was made with thecomponents in the table below. The encapsulated epoxy resin was the lastcomponent added to the formulation. The epoxy resin was EPON 828, adifunctional bisphenol A/epichlorohydrin derived liquid epoxy resinavailable from Resolution Performance Products. It was encapsulated indouble walled gelatine/PMU capsules. Photomer 4039 is an ethoxylated (3)phenol monoacrylate (available from Cognis). Ebecryl 3500 is an acrylateepoxy oligomer (available from UCB/Radcure) used for speed of cure.Ebecryl 270 is an aliphatic urethane acrylate oligomer (also availablefrom UCB/Radcure) used for enhancing flexibility. Flex Resin II(available from Henkel Loctite) is used for enhancing flexibility. Thecomponents other than the microencapsulated epoxy are given in amountsbased on w/w of the composition excluding the microencapsulated epoxy.The part of the composition excluding the epoxy microcapsules(hereinafter “acrylate portion”) and the epoxy microcapsules werecombined in the following ratio by weight: 59.41 parts acrylate potionto 40.59 parts epoxy microcapsules. This ratio is employed in allExamples.

Example 1

TABLE 1 % weight of components in the part of the composition excludingthe microencapsulate epoxy component Component % weight Photomer 403921.53 N,N Dimethylacrylamide 13.78 Ebecryl 3500 30.14 Ebecryl 270 14.64Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide 1.73 1-Hydroxycyclohexylphenyl ketone 4.3 Polymethyl methacrylate granules (PMMA) 1.96 Silica3.3 Dipyr 8.62

The viscocity of this composition excluding the microencapsulated epoxycomponent, when measured with a Haake Roto Visco 1, c60/1° Cone, shearrate 244 s⁻¹, was 1,326 mPas.

Example 2

TABLE 2 % weight of components in the part of the composition excludingthe microencapsulate epoxy component Component % weight Photomer 403921.96 N,N Dimethylacrylamide 14.06 Ebecryl 3500 30.74 Flex Resin II14.93 Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide 1.761-Hydroxycyclohexyl phenyl ketone 4.39 Silica 3.37 Dipyr 8.79

The viscocity of this composition excluding the microencapsulated epoxycomponent, when measured as in Example 1, was 731 mPas.

Application of Product

A composition according to each of the Examples above (including themicroencapsulated epoxy component) was applied to threaded bolts. Thecomposition was irradiated for 3 to 4 seconds at an intensity of 60mW/cm² provided by a medium pressure iron doped mercury vapour lamp.Irradiation of coated parts left a dry to touch coating.

A composition according to each of the Examples above has a shelf lifeof at least 6 months at 5° C. The microencapsulated epoxy component hasan indefinite shelf life. A composition according to the Examples aboveincluding the microencapsulated epoxy component has a shelf life of atleast one week. The composition can be stored for use in either aone-part or a two-part format. When formulated as a two-partcomposition, one part of the composition may comprise a compositionaccording to each of the Examples above and a second part will usuallycontain the microencapsulated epoxy component. Threaded bolts which havehad a composition according to the Examples above including themicroencapsulate epoxy component applied to them and UV cured have ashelf life of at least one year. Break/prevail values in the region of20 Nm have been recorded from assemblies of M10 mild steel black oxidebolts and M10 mild steel nuts following a 72 hour cure of thecomposition according to each of the Examples above (including themicroencapsulated epoxy component) at room temperature.

It is appreciated that certain features of the invention, which are, forclarity, described in the context of separate embodiments, may also beprovided in combination in a single embodiment. Conversely, variousfeatures of the invention which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination.

The words “comprises/comprising” and the words “having/including” whenused herein with reference to the present invention are used to specifythe presence of stated features, integers, steps or components but doesnot preclude the presence or addition of one or more other features,integers, steps, components or groups thereof.

1. An apparatus for the application of a composition curable byirradiation to a fastener having an externally threaded stem,comprising: a coating section, including: a coating conveyor forconveying the fastener in a horizontal position to an applicationstation, the coating conveyor comprising a rail parallel to, andhorizontally separated from, an application surface and a first endlessdrive element vertically separated from the rail and the applicationsurface, wherein the fastener stem spans the rail and the applicationsurface and is rotated over the rail and application surface and underthe first endless drive element, and the application station from whichthe composition is dispensed onto the application surface, wherein thefastener stem is rotated through the dispensed composition by rollingmovement over the rail and the application surface and under the firstendless drive element for application of a circumferential band ofcomposition to the fastener stem; and a curing section, including: acuring conveyor for conveying the fastener in a horizontal position toan irradiation station, the curing conveyor comprising two, parallel,horizontally separated rails and a second endless drive elementvertically separated from the rails, wherein the fastener stem havingthe circumferential band of composition thereon spans the rails and isrotated over the rails and under the second endless drive element as itmoves toward the irradiation station; and the irradiation station for atleast partially curing the composition applied to the fastener stem. 2.An apparatus according to claim 1 wherein the composition is an at leasttwo stage curable composition; the curable composition having a firstcure stage which is activatable by irradiation, and a second cure stagewhich is curable to secure the fastener in a fastening position.
 3. Anapparatus according to claim 1 further comprising a fastener feeder forfeeding fasteners one by one to the coating conveyor.
 4. An apparatusaccording to claim 1 wherein the coating conveyor extends through theapplication station.
 5. An apparatus according to claim 1 wherein theapplication surface is a horizontal surface of a coating block.
 6. Anapparatus according to claim 1 wherein the vertical separation betweenthe first endless drive element and the application surface can bealtered by a user.
 7. An apparatus according claim 1 further comprisingtemperature control means for regulating the temperature of the fastenerprior to application of composition thereto.
 8. An apparatus accordingto claim 1 wherein the apparatus further comprises a transfer mechanismfor transferring the fasteners from the coating conveyor to the curingconveyor.
 9. An apparatus according to claim 1 comprising a supplysystem supplying curable composition to the application surface.
 10. Anapparatus according to claim 1 wherein the irradiation station comprisesa UV light source for irradiating applied composition with UV light. 11.An apparatus according to claim 1 wherein the irradiation stationcomprises a radiation source housed in an enclosure which emitsradiation through an aperture therein.
 12. An apparatus for applying anat least partially cured composition to a fastener having an externallythreaded shank, comprising: a coating conveyor comprising two spacedsupports defining a first fastener feed plane and a coating conveyordrive element spaced from the first plane, wherein the fastener shankcan be disposed between the two spaced supports and the coating conveyordrive element and the fastener can be rolled on the two spaced supportsfrom a fastener feed position toward a coating station by contact withthe coating conveyor drive element; the coating station comprising asupport spaced from a coating block and a coating station drive elementspaced from the coating block, the coating block comprising anapplication surface onto which a curable composition can be dispensed,wherein the fastener shank can be disposed between the coating block andthe coating station drive element and the fastener can be rolled on thesupport and the application surface by contact with the coating stationdrive element as it moves through the dispensed curable composition; acuring conveyor comprising two spaced supports defining a secondfastener feed plane and a curing conveyor drive element spaced from thesecond plane, the curing conveyor extending from a coated fastener feedposition toward a fastener exit position, wherein the coated fastenershank can be disposed between the two spaced supports and the curingconveyor drive element and the fastener can be rolled on the two spacedsupports by contact with the curing conveyor drive element as it movestoward the exit position; and a radiation source capable of providing abeam of energy intersecting the second plane and the coated fastenershank.
 13. The claim of 12 wherein the first fastener feed plane ishorizontal.
 14. The claim of 12 wherein the first and second fastenerfeed planes are coextensive.
 15. The claim of 12 further comprising afastener transfer mechanism between the coating conveyor and the curingconveyor.
 16. The claim of 12 further comprising a transfer conveyorcomprising two spaced supports defining a transfer fastener feed planeand a transfer drive element spaced from the transfer plane, thetransfer conveyor extending from the coating station to the curingconveyor, wherein the coated fastener shank can roll between the twospaced supports and the transfer drive element as it moves toward thecuring conveyor.
 17. The claim of 12 wherein the coating conveyor twospaced supports and curing conveyor two spaced supports are fixed andthe coating conveyor drive element and the curing conveyor drive elementare different, movable, endless loops of material.
 18. The claim of 12wherein the coating conveyor two spaced supports and curing conveyor twospaced supports are fixed, the coating conveyor drive element moves at afirst speed and the curing conveyor drive element moves at a secondspeed different than the first speed.
 19. The claim of 12 wherein thedistance between the first plane and the coating conveyor drive elementand the distance between the second plane and the curing conveyor driveelement are independently adjustable.